Humidity control for oven chamber

ABSTRACT

A combination steam and dry oven has an integral boiler that is located inside the oven cavity. The combination oven can be operated as a forced-air convection oven, a force convection oven circulating superheated steam, or a steamer near the boiling temperature of water. Sensors in the oven supply information to a microprocessor that controls heating elements to maintain an oven temperature within 10° Fahrenheit. The oven functions by circulating superheated steam by blowing its circulating gas over the surface of the internal boiler, which is protected from contamination by a baffle. Sensors of the level of water in the boiler assure that the water level either stays within predetermined limits or else shuts down the oven if the water level is out of limits. Tray stops keep foods and the trays containing them away from the walls of the oven to permit free circulation of air or superheated steam. Sensors of water temperature in the boiler and gas temperature in the circulating gas permit the control of relative humidity when the oven is used to proof dough or hold cooked food at a relatively low temperature. Control of the temperature of water in the boiler is aided by blowdown and replacement if the temperature becomes excessive. The oven may stand alone or it may be stacked as a combination of units.

This is a division, of application Ser. No. 050,708, filed May 14, 1987now patent 4,851,644.

BACKGROUND OF THE INVENTION

This invention relates to cooking ovens. In particular, it relates toovens for forced convection cooking with superheated steam, saturatedsteam, or heater air.

The art of cooking an object in an oven involves raising the coretemperature of the object to a desired value while controlling thetemperature and other conditions on the outside of the object to achievea desired surface appearance. When two or more objects are placed in anoven to be cooked, an additional problem arises. That is the problem ofmaintaining uniformity among objects that are cooked. As time passes inthe cooking cycle of a particular object, it is necessary to arrangesome kind of circulation of heat to prevent stratification in the oventhat light lead to uneven cooking of different objects or of differentregions of the same object.

One oven function that is sometimes used to assist in cooking is tocirculate steam with or in place of the hot air in the oven. The steamis produced by a boiler that typically is located outside the oven.Water is piped into the boiler and is heated by a local unit to generatesteam that is conveyed into the oven for circulation. While it is commonto specify a maximum level of dissolved solids in the water to be usedin such a boiler, a level that normally requires softened water, itstill is necessary to clean the boiler periodically to remove depositedminerals from the water as well as removing any contaminants fromcooking.

Many ovens that circulate steam to cook can also be operated assteamers, holding or circulating saturated steam to thaw frozen foods,cook vegetables, or maintain cooked foods hot and ready to serve. Such ause of the oven produces condensate which must be removed from the ovenwithout interfering with the cooking or steaming function.

Another problem in the operation of cooking ovens is that of temperaturecontrol. It is desirable to have the temperature uniform in throughoutthe oven, and uniform as a function of time after the oven has come upto a particular temperature. It is not uncommon for the control range ofthe temperatures in both commercial and residential ovens to vary asmuch as 50° F. in both space and time. Variations in space can beminimized by circulating air with a blower or the like and by designingthe interior of the oven to minimize the blockage of flow by pans andother containers of foods to be cooked. Variations of temperature withtime are functions of temperature sensors and controllers that are usedin response to them.

A further problem in cooking arises from the fact that cooking cyclessometimes require temperature changes. In such a case, it is necessaryto have some means of storing a desired temperature control level for aparticular time and a different temperature control level for adifferent period of time. Information such as this is best handled by amicroprocessor with associated memories.

A complete kitchen, industrial or residential, may call for theprocessing of dough for bread or pastries. This includes the functionknown as proofing, which is the holding of dough at a controlledtemperature and possibly also at a controlled humidity to enable yeastto work and raise the dough. The control of both temperature andhumidity enables an oven to be used as a proofing oven.

In kitchens, industrial or residential, it is often desirable to cookovernight and hold cooked items ready to be used on a following day.This normally calls for a relatively high cooking temperature for apredetermined time, followed by at lower temperature. It is oftenconvenient when holding at the lower temperature to be able to controlthe humidity to prevent excessive drying of cooked items during theholding period.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a better oven forcooking.

It is a further object of the present invention to provide a novel oventhat cooks by forced circulation of air.

It is a further object of the present invention to provide a novel oventhat cooks by forced circulation of superheated steam.

It is a further object of the present invention to provide a novel oventhat functions as a steamer.

It is a further object of the present invention to provide a novelcombination oven that cooks with dry air, superheated steam, orsaturated steam.

It is a further object of the present invention to provide a novelcombination steam oven, dry oven, and steamer that is controlled by amicroprocessor.

It is a further object of the present invention to provide a novel ovenwith precise temperature control in time.

It is a further object of the present invention to provide a novel oventhat provides precise temperature control in space.

It is a further object of the present invention to provide a novel ovenhaving a boiler inside the oven cavity.

It is a further object of the present invention to provide a novel ovenhaving an internal boiler with heating elements that are readilyremovable from inside the oven cavity.

It is a further object of the present invention to provide a novel ovenwith doors that are readily convertible to open either from left orright.

It is a further object of the present invention to provide a novel ovenwith a seal that prevents the entry of air into the oven and the escapeof steam from the oven below a certain pressure.

It is a further object of the present invention to provide a novel ovenusing steam or cooking or warming that includes a boiler inside theoven.

It is a further object of the present invention to provide a novel ovenwith an internal boiler that is protected against contamination fromdripping food.

It is a further object of the present invention to provide a novel oventhat can produce controlled temperatures and humidities.

It is a further object of the present invention to provide a novelforced convection oven with a fan blade that is readily removable.

Other objects will become apparent in the course of a detaileddescription of the invention.

A combination steam and dry oven has in integral boiler that is locatedinside the oven cavity. The combination oven can be operated as aforced-air convection oven, a forced convection oven circulatingsuperheated steam, of a steamer circulating saturated steam. Sensors inthe oven information to a microprocessor that controls heating elementsto maintain an oven temperature within 5° Fahrenheit or less. The ovencirculates superheated steam by blowing its circulating gas over thesurface of the internal boiler, which is protected from contamination bya baffle. Sensors of the level of water in the boiler assure that thewater level stays within predetermined limits. Tray stops keep foods andthe trays containing them away from the walls of the oven to permit freecirculation of air or superheated steam. Sensors of water temperature inthe boiler and gas temperature in the circulating gas permit the controlof relative humidity when the oven is used to proof dough or hold cookedfood at a relatively low temperature. Control of the temperature ofwater in the boiler is aided by blowdown and replacement if the watertemperature becomes too high. The oven may stand alone or it may bestacked as a combination of multiple units.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric front view of a specific embodiment of thecombination oven of the present invention.

FIG. 2 is a cut-away front view of a specific embodiment of thecombination oven of the present invention.

FIG. 3 is a partially cut-away left side view of a specific embodimentof the combination oven of the present invention.

FIG. 4 is a rear view of a specific embodiment of the combination ovenof the present invention.

FIG. 5 is in isometric view of the boiler of a specific embodiment ofthe combination oven of the present invention.

FIG. 6 is a cut-away view of the oven door from inside the oven of FIG.1.

FIG. 7 is a bottom view of the oven door of FIG. 6.

FIG. 8 is a cut-away side view of a portion of the oven door of FIG. 6.

FIG. 9A is front view of the spring of FIG. 6.

FIG. 9B is a side view of a specific embodiment of a latch bullet.

FIG. 10 is in expanded view of a specific embodiment of the controlpanel of the combination oven of FIG. 1.

FIG. 11 is a functional block diagram of a circuit for powering andcontrolling a specific embodiment of the combination oven of the presentinvention.

FIG. 12 is a flow chart of a specific embodiment of the power-upsequence of the combination oven of FIG. 1.

FIG. 13 is a flow chart of a specific sequence of operation in the ovenmode.

FIG. 14 is a flow chart of a specific sequence of operation in thecombination oven sequence.

FIG. 15 is a flow chart of a specific sequence of operation in the steammode.

FIG. 16 is a flow chart of a specific sequence of operation in the holdor proof mode.

FIG. 17 is a flow chart illustrating a specific process of control ofboiler water level.

FIG. 18 is a flow chart a specific process of operation of the cool-downmode for the combination oven.

FIG. 19 is a combination front, side and bottom view of the shroud 60 ofthe present invention.

FIG. 20 is a combination top, side, and end view of a shelf 72 of FIG.2.

FIG. 21 is a sectional view through the center of the shaft of theblower 82 of FIG. 3.

FIG. 22 is a connection diagram showing the means of achieving differentlevels of heating power using the same relays for single-phase power andthree-phase power.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is an isometric front view of a specific embodiment of acombination oven 20 of the present invention. In FIG. 1, a door 22 isshown with a hinge on the left and a handle 24 on the right. It will beseen later that the door 22 can be reversed in the field to place thehandle 24 on the left and the hinges 26 on the right for use withvarious kitchen layouts. A control panel 28 includes controls and visualdisplays that will be described later in detail. Legs 30 are provided toallow the oven 20 to function as a self-standing unit, or thecombination oven 20 may be used without legs. In addition, twocombination ovens 20 can be stacked one above the other in a combineddouble unit. These are matters of design choice.

FIG. 2 is partially cut-away front view of the combination oven 20 ofthe present invention. As in FIG. 1, the door 22 in FIG. 2 has thehandle 24 at the right and the hinges 26 at the left. The control panel28 includes a key pad 40, a number of push buttons 42 and a dial 44 thatcan be used to enter control data. A display 46 shows cooking time,diagnostic information, and other information that can be programmed bythe operator. A display 48 shows the temperature selected for cooking.The legs 30 are about four inches long, which provides clearance toclean under the combination oven 20. A drain 50 carries condensate andliquid wastes to the sewer.

An oven chamber 52 is the cooking space in the combination oven 20. Theoven chamber 52 includes racks 54 and 56. The rack 54 is secured to aninside wall 58 of the oven chamber 52, and the rack 56 is secured to ashroud 60 which defines a wall of the oven chamber 52 and a plenum 62.The shroud 60 is shown below in more detail. The racks 54 and 56 includespacers 55 and 57, respectively. The spacers 55 and 67 projectvertically to keep shelf 72 away from the wall 58 and the shroud 60.This improves the circulation of air or steam in the oven chamber 52,which is in the direction of arrow 64. The shroud 60 causes some of theair or steam to blown boiler past a hollow 66, which is formed as anintegral part of the oven chamber 52. FIG. 2 also shows a reed switch 67which is disposed in the combination oven 20 so as to be concealed bythe stainless-steel exterior of the combination oven 20. It will be seenbelow that the door 22 includes a magnet (see FIG. 6) to operate thereed switch 67 to provide in indication that the door 22 is closed oropen. A second reed switch (not shown) is located in a correspondingposition in the combination oven 20 in the right side of door 22. Theone of the two reed switches that is on the side of the door handle 24is used to signal closure of the door 22. The magnet operates the reedswitch 67 or the reed switch that is not shown through the non-magneticstainless steel of the door 22 and the combination oven 20.

Water in the boiler 66 is heated by a plurality of heating elements 68,of which only one is visible in FIG. 2. A baffle array 70 deflects anydrippings from the stream of heated air or steam following the arrow 64from contaminating the water in the boiler 66, and also keeps waterinside the boiler 66 and out of the rest of the oven chamber 52 andplenum 62. At the same time, the boiler 66 is disposed so as toevaporate steam into the flow in the direction of the arrow 64 andthereby control humidity or steam level in the oven chamber 52. In thisway, food placed in trays or the like on one or more of the shelves 72is exposed to desired conditions of heat and humidity. It can also beseen from an inspection of the racks 54 and 56 and the shelf 72 thattrays of food placed on the shelf 72 will be spaced away from the insidewall 58 and the shroud 60 by the spacers 55 and 57 so as to facilitatecirculation of heated air or steam around the trays of food.

FIG. 3 is a partially cut-away side view of the combination oven 20 asseen from the left side of FIG. 1. In FIG. 3, wall 80 is protected fromthe cooking temperatures inside the combination oven 20 the insulation34 which in turn is protected from conditions in the oven chamber 52 bythe inside wall 58. A blower 82 circulates air and steam through theshroud 60 and into the plenum 62 of FIG. 2 from the oven chamber 52,then out at the top and bottom of the plenum 62 and back into the ovenchamber 52. A screw 84 in a blower 82 is placed to serve as a wheelpuller of the blower 82 from its shaft, facilitating maintenance of theoven 20. Details of this screw 84 are shown below.

The blower 82 is placed to blow air, steam or both substantiallyradially through heating elements 86, 88 and 90. Three such heatingelements are shown because it is convenient to equip the combinationoven so that it can be heated either by single-phase or three-phaseelectrical systems. The heating elements 86, 88 and 90 are preferablyspecified for maximum voltages of 208 volts or 240 volts, and thecombination oven may be operated either single-phase or three-phase, asshown below. The use of three discrete heating elements provides maximumflexibility in making such connections. It is convenient to makeindividual heating elements in serpentine or wave shapes which are thenbent to form arcs of circles.

Referring to FIG. 3, a preferred array of heating elements 86, 88 and 90is shown in which each such heating element spans approximately 240° ofarc, centered about the blower 82. Identically shaped elements arereadily bent to the slightly different radii indicated. Three elementsare combined to form two circumferential rings through which air isblown. As a result, when all three heating elements 86, 88 and 90 arepowered, air from the blower 82 is heated by contact with two heatingelements over the entire circulating circumference. Air then contacts aheated element over 240° of circumference. On low heat, only one suchelement is used. In either case, the span of the elements provides forin even distribution of heat in the air stream that is produced by theblower 82.

In the illustrated embodiment of the oven of the present invention thathas been built, the heating elements 68 of FIG. 2, which were used toheat water in the boiler 66, comprised three helical elements, eachrated at three kilowatts. The heating elements 86, 88 and 90 of FIG. 3were each rated at two and one quarter kilowatts. In any mode in whichstream was being used, full power, nine kilowatts, was applied initiallyto the heating elements 68 of boiler 66 with no power being supplied toheating elements 86, 88, and 90. When water in boiler 66 reached withina few degrees of boiling, connections to the heating elements 68 werechanged depending upon the mode selected. In the combo mode, connectionswere switched to supply one and one half kilowatts to the boiler. Thiswas done by placing two heating elements 68 in series. If the oven wasto be operated as a steamer, the heating elements 86, 88, and 90 werenot energized, and the blower 82 was operated continuously to circulatesaturated steam in the oven. In contrast, if the oven was operated as acombo oven, circulating superheated steam, the heating elements 86, 88and 90 were cycled between levels of six and three quarter kilowatts andoff in response to sensed temperatures as compared with a controlsetting.

FIG. 3 shows a probe 92 that projects into the oven for sensingtemperatures. The probe 92 contains a resistive thermal device (RTD), athermally sensitive resistor that is typically used as an element in avoltage divider to provide a signal proportional to temperature. Othertemperature transducers, such as thermocouples, thermistors, bimetallicdevices or the like could be used. Other such probes are shown inanother view of the combination oven 20. A probe 94 is inserted in adrain line 96 to measure the temperature in the drain line 96. As spraynozzle 98 is connected into the drain line 96 to maintain a water sealin the drain line 96 and to condense steam from the combination oven 20.

FIG. 4 is a partially cut-away rear view of the combination oven 20. InFIG. 4, a solenoid valve 100 includes a hose connection 110 forsupplying water from an external source. The solenoid valve 100 supplieswater through a line 112 to the boiler 66 of FIG. 2. A line 114 is takenfrom the solenoid valve 100 to the drain line 96. A fitting 116 isattached to the boiler 66 of FIG. 2 to connect it to a drain hose 118.The drain hose 118 is connected to drain line 96 through clamp valVe120. This is a solenoid-operated valve that pinches drain hose 118 bydrawing a pinch bar 122 against a stop. This provides the advantages ofa valve that is subject to minimum amount of interference from thebuild-up of salts from the boiler water, that is self-cleaning inoperation, and that permits ready removal and replacement of the drainhose 118. The drain hose 118 is held in place by hose clamps 124 and 126which facilitate its removal or replacement.

FIG. 5 is a perspective view of the boiler 66 of the combination oven ofthe present invention. FIG. 5 shows heating elements 140 and 142, inaddition to the heating element 68 that is visible in FIG. 2. A wall 144of the boiler 66 represents a continuation of the oven chamber 52 andthe plenum 62 of FIG. 2, so that the boiler 66 is an integral part ofthe interior of the combination oven 20. In FIG. 5, the baffle array 70of FIG. 2 is seen to comprise several elements. One of these is a baffleplate 146, which is secured within the boiler 66 by bolts 148 and 150.This serves to hold heating elements 68, 140 and 142 in place. Thebaffle plate 146 also minimizes effects of the splashing that occurswhen water in the boiler 66 is bubbling vigorously. A tab 152 in thebaffle plate 146 covers a water temperature sensor which is not shown. Aslot 154 in the baffle plate 146 permits passage of the level sensor 74.Level control means 282 (discussed hereinafter) is connected to levelsensor 74 for controlling the means for supplying water (solenoid valve100) and the means for draining water (solenoid value 120) to control alevel of water in the boiler. Bars 156 and 158 support a baffle cover160, which is removed by the use of a handle 162. The baffle cover 160includes bars 164 and 166, which are supported by bars 156 and 158. Anedge 168 of baffle cover 160 is disposed within the opening of a channel170, which is affixed to a rear wall 172 of the boiler 66. The assembledposition of the baffle cover 160 within the channel 170 is readily seento form the baffle array 70 of FIG. 2. This comprises a labyrinth thatprevents liquid water from entering the plenum 62 of FIG. 2, andminimizes entry of cooking drippings into the boiler 66. The cover 160slopes toward the center of the oven chamber 52 to direct cookingdroppings toward the drain 50 of FIG. 2.

One method of cleaning the combination oven 20 comprises removing thebaffle cover 160 of FIG. 5 and placing a cleaning solution in the boiler66 to a level that at least covers heating elements 68, 140 and 142. Thecleaning solution may ne vinegar, sulfamic acid, or a commercialdegreasing compound. Vinegar is particularly effective at removing limedeposits in the boiler, while sulfamic acid is particularly effective atdegreasing the interior of the oven. The oven is cleaned by applying thepower to heating elements 68, 140 and 142, while circulating theresulting fumes through the oven. The boiler 66 is then drained by theoperating clamp valve 120 of FIG. 4 which drains the boiler 66 throughthe fitting 116. The boiler may then be flushed by water admittedthrough the line 112. Entry of water to the boiler 66 and its dischargeto the drain line 96 of FIG. 4 are also controlled in response to anumber of conditions that will be described below.

FIG. 6 is a view of the door 22 of FIG. 1 from inside the combinationoven 20 of FIG. 1, and FIG. 7 is a partial sectional bottom view of thedoor 22 of FIG. 6. In FIG. 6, a channel 180 covers an opening 182 whichexposes a portion of a spring 184. The channel 180 also covers a magnet186, which operates a reed switch to indicate that the door is open.

As shown in FIG. 6, the channel 180 is on the left and the hinge 26 ison the right. Reversal of the door is effected by removing a hinge pin188, a hinge plate 190 and the channel 180, to which the spring 184 isattached. The magnet 186 is held in place by the channel 180. A hingeplate 190 is installed on the left side of the oven, the plate 180 isturned upside down from its position in FIG. 6, placing the magnet 186at the top in FIG. 6, and the door 22 is rotated 180° to place the hinge26 on the left, the plate 180 on the right, and the magnet 186 at thebottom in the right. The hinge pin 188 is then inserted from the top.The handle 24 is also turned upside down.

A gasket 192, located around the edge of the door 22 as shown, is madeof a resilient material, such as silicone rubber or the like, that willwithstand oven temperatures and still seal the oven by coming intoengagement with the edges of oven chamber 52 of FIG. 2. In FIG. 7, thegasket 192 is seen to have a U-shaped form with a tab 194 that holds thegasket 192 in place. A contact region 196 is molded so as to be thinnerin cross-section than the rest of the gasket 192. This facilitatesbending of the gasket about a rounded lip 198, which protrudes from thecombination oven 20 as an extension of the inside wall 58 of FIG. 2 tomake a seal with the gasket 192. The rounded lip 198 is thinner than thewidth of the gasket 192, so that when the door 22 is closed, a portionof the gasket 192 is wrapped partly around the rounded lip 198, making aseal. This keeps air out of the oven chamber 52 and steam in. However,any buildup of pressure in the oven chamber 52 above predeterminedamount is readily vented as the gasket 192 yields. The inside wall 58 isidentified for reference, but rounded lip 198 is disposed in asubstantially rectangular pattern as seen from the front of thecombination oven 20 to engage the gasket 192 and make a seal. The shapeof the gasket 192, as shown in cross-section in FIG. 7, makes itpossible to form gasket 192 as a single molding without the need to usere-entrant mold parts. This is in contrast to the typical gasket whichis molded as tubing and is cut and joined at the corners. The joint,made by vulcanizing or the like, tends to change the characteristics ofsuch gaskets and make them more difficult to seal. The single-piecemolded gasket 192 is free of such joints, which contributes to a moreeffective oven seal. Replacement of the gasket 192 and cleaning of thedoor 22 are both facilitated by removal of the hinge pin 188, whichallows the door 22 to be removed from the combination oven 20.

FIG. 8 is an expanded cut-away side view of a portion of the door 22,FIG. 9A is a front view showing the spring 184 of FIG. 8, and FIG. 9B isa side view of a the latching bullet 214. In FIGS. 8, 9A and 9B, a screw200 is attached to the door 22 to secure the spring 184 to a slidingplate 204 in door 22 while permitting rotation of the spring 184 aboutthe center of the screw 200. The plate 204 is also free to pivot about ascrew 205. This rotation of the spring 184 allows the spring 184 to makeup for considerable amounts of misalignment of the door with respect tothe latching bullet 214 that is attached to the combination oven 20 tosecure the door 22. The handle 24 is attached to a cam 202 and to thesliding plate 204, which permits relative motion of the handle 24 andthe cam 202 with respect to the door 22. Thus, when handle 24 is movedin the direction of in arroW 206, the cam 202 is forced between prongs208 and 210 of the spring 184. This spreads the spring 124 to releasethe door. The insulation 34 in the door 22 is placed throughout theinterior of the door 22 except in a region occupied by the spring 184and the cam 202. Structural support and separation of parts of the door22 is maintained by a plurality of spacers 212 and by the insulation 34,a structurally rigid piece of insulation board.

FIG. 9B shows the bullet 214 which is fixed in place on the front of theoven 20 to engage the spring 184. Groove 216 in the bullet 214 engagesthe spring 184, which is spread by the cam 202 to release the spring 184from groove 216 when the handle 24 of FIG. 8 is lifted. Threads 218 ofthe bullet 214 are used to secure the bullet 214 to the front of thecombination oven 20. If the door 22 is changed to open in a differentdirection, the bullet 214 will have to be moved to engage the spring 184on a different side. A mounting hole for the side of the door that isnot used is covered by the hinge plate 190 of FIG. 6.

FIG. 10 is an expanded view of the control panel 28 of FIG. 1. In FIG.10, the key pad 40 comprises a complete set of numbers and also a startbutton 220 and a clear button 222. The time display 96 displays hoursand minutes, with the hours separated by a colon that flashes once persecond to indicate that the timer is operating. The display on the timedisplay 46 is cleared either by timing out or by the use of a clearbutton 222. Normal operation of the oven will comprise entering adesired cooking time by the use of the numerical keys of the key pad 40after the combination oven 20 has reached a preset cooking temperatureand displayed a "ready" light. Use then of the start button 220 begins acountdown so that a time display 224 shows remaining time to cook. It isalso possible to use the time display 224 to display elapsed time.

A set of push buttons 42 provides for the selection of a mode and forturning combination oven 20 on and off. Thus, the push buttons 42include an on-off switch 226 and a steam select button 228, a comboselect button 230 and an oven select button 232. When a temperature andmode are selected and the cold combination oven 20 is turned on by theuse of the push buttons 42, a wait light 234 will normally indicate thatthe combination oven 20 is heating to the desired temperature. A readylight 236 will then light to indicate that the desired temperature hasbeen reached. A hot light 238 will normally provide in indication onlywhen the selected temperature has been changed to a lower value for inoven that is already hot. That temperature is selected by turning thedial 44 to select the temperature that appears in the display 48. Aservice light 240 provides an indication that a diagnostic program hasdetected one or more malfunctions in the operation of the oven.

FIG. 10 also shows controls for features that are optional, but that addgreatly to the versatility of the combination oven 20. A holdtemperature dial 242 allows the selection of a holding or proofingtemperature that is displayed in a display 244. A humidity dial 246allows the selection of a humidity range that is displayed on a display248. The temperature and humidity selected by the dials 242 and 246 areuseful in two situations. First, temperature and humidity may be set bythe dials 242 and 246, respectively, and a time, a temperature and acooking mode may be selected by the key pad 40, the dial 44, and one ofthe select buttons 228, 230 or 232. When this happens, the combinationoven 20 will perform selected to cook food until the time displayed onthe time display 46 reaches zero. The oven 20 will then hold food at atemperature and humidity selected by the dials 242 and 246. Thistemperature is typically lower than the cooking temperature, to keepcooked food ready to serve. A second mode of operation is use of theoven to proof dough. This is allowing dough to rise under conditions ofcontrolled temperature and humidity. To proof, the desired temperatureand humidity are selected on the dials 242 and 246, and the start button220 is pressed. This operates the oven under the control of the selectedtemperature and humidity without first going through a cooking stage. Ineither case, the humidity is controlled by use of measurementstemperature of boiler water and circulating air. These are analogous toa wet- and dry-bulb measurement of temperature, which is a well-knownway of measuring relative humidity.

FIG. 11 is a functional block diagram of a specific microprocessorarrangement for controlling the oven 20 of the present invention. InFIG. 11, manual inputs 260 and automatic inputs 262 representrespectively the setting of switches, knobs, and the like, and thegeneration of inputs from sensors and automatically operated switches.Both outputs are taken to a multiplexing analog-to-digital (A/D)converter 264, which generates data inputs to a microcomputer 266. Themicrocomputer 266 is served by a read-only memory (ROM) 268, whichstores an operating program for the microcomputer 266. A random-accessmemory (RAM) 270 provides volatile memory for the microcomputer 266, andan electrically erasable programmable read-only memory (EEPROM) 272supplies non-volatile memory for such functions as repeating the lastprevious cooking cycle. This enable a chef, for example, to enter acooking time that is stored so that when he wishes to repeat the samecooking cycle, he need only load the oven, close the door, and press thestart button. Outputs from the microcomputer 266 are taken to adigital-to-analog (D/A) converter 274 where they provide signals thatare taken to control displays 276, a heater control 278, a fan control280, a water-level control 282, and in alarm 284. Details of operationof control systems will be disclosed in the flow charts that follow.

FIG. 12 is a flow chart of the sequence of operations controlling theoven 20 after power-up. In FIG. 12, block 290 results from operating theon switch. A decision block 292 tests for overtemperature. Anovertemperature sensor in the oven chamber and another overtemperaturesensor in the plenum chamber will direct a block 294 to turn the poweroff if overtemperature is detected. If it is not, a decision block 296tests for an open door. If the door is open, a block 298 cuts heatingpower and the oven stands by for further instructions. If the door isclosed, a mode switch 300 calls for the selection of a block 302, steam;a block 304, combo; or a block 306, oven.

FIG. 13 is a flow chart of operation in the oven mode. In FIG. 13, ablock 310 is engaged by selecting oven and setting a temperature bymeans of the oven select button 232 and the dial 44 of FIG. 10. A block312 causes the blower 82 of FIG. 3 to turn on. A decision block 314 thentests for whether the temperature is in range. If the temperature is notin range, a decision block 316 tests to see whether the temperature islow. If the temperature is low, a block 318 turns on the "wait" light234 and a block 320 calls for high oven heat. Operation continues withthe heat high and the "wait" light 234 in. If the temperature is not inrange and is not low, a decision block 322 tests to see if thetemperature is high. If the temperature is neither low nor high, anerror indication 324 switches control to a service routine. If thetemperature is high, a block 326 switches the oven heat off and a block328 calls for the "hot" light 238, which stays on until the temperatureis no longer high. If the decision block 314 indicates that thetemperature is in range, a block 330 switches the oven heat to low, anda block 332 calls for the "ready" light 236. These conditions willcontinue until the block 332 receives a power-off indication, in whichcase control exits to an off circle 334. The power-off switch 226 may beoperated manually, or the "off" condition may be operated by timeout ofthe timer.

FIG. 14 is a flow chart of operation in the combination oven sequence.This is the mode in which steam is superheated when it is circulatedthrough the heating elements 86, 88 and 90 by the blower 82. In FIG. 14,a block 340 indicates that the "combo" mode has been selected. This isdone by pushing "combo" button 230 and pressing the on button 226. Ablock 342 calls for the blower 82 to run. A block 344 indicates thatcooking time should be set, but this is not necessary. The "combo" modecomes to "ready" without setting a cooking time. A decision block 346then tests the boiler temperature. If the temperature is less than apredetermined value, here indicated as 205° F., a block 348 calls forboiler heat to be at full power (9 kilowatts) and a block 350 calls fora "wait" light 234. The predetermined temperature that affects thechange of the decision block 346 may be set in the program by theprogrammer, based upon parameters such as the altitude at which the ovenis to operate, or it may be determined adaptively within the oven as apredetermined number of degrees below the ambient boiling temperature.However the limit is set, when the decision block 346 determines thatthe boiler temperature has reached or exceeded the preset temperature, ablock 352 turns boiler heat off. A decision block 354 then tests to seewhether the oven chamber 52 is at the set temperature. If it is not, ablock 356 tests to see whether it is over the set temperature. If it isnot, a block 357 calls for high oven heat and a block 358 calls for the"wait" light 234. This condition continues until the block 354determines that the oven chamber 52 is at the set temperature. In thealternative, if the temperature setting has been reduced for a hot oven,the decision blocks 354 and 356 will indicate that the oven chamber 52is over the set temperature. In this case, a block 360 will turn theoven heat off and a block 362 will light the "hot" light 238.

One or the other of the two loops just described will continue until theoven chamber 52 reaches its set temperature, at which time control exitsfrom the decision block 354 to a block 364. This sets the oven heat tolow. A block 366 lights the "ready" light 236. If cooking time has notbeen set at the block 344, the oven chamber 52 will maintain the presettemperature by looping in the control blocks just described. This iseither waiting mode, awaiting the insertion of food into the oven, or itis a cooking mode. The combo oven can be used without using the timer.If it is desired to be used with the timer, then a block 368 starts thetimer countdown. This is engaged by setting a time on the timer 46, if atime has not been set, and by pushing the "start" button 220. A decisionblock 370 then tests whether the timer has timed out. If it has not,control returns to the cooking cycle. If the timer has timed out, adecision block 372 tests whether the "hold" is set by dial 242. If itis, control passes through a block 373 to the "hold" mode. If "hold" isnot set, or if the oven does not include the "hold" option, the decisionblock 372 passes control to a block 374, which turns off the oven powerto the heating elements and the blower. A block 376 sounds a buzzer fora predetermined time interval, and a stop circle 378 indicates that theoven has stopped its cooking cycle.

FIG. 15 is flow chart of operation in the steam mode. When steam isselected, as indicated by a selection block 380, a block 382 calls forthe blower 82 to operate. A block 384 calls for the setting of a cookingtime, and a decision block 386 tests to see if boiler temperature is atthe boiling temperature. If it is not, a block 388 calls for boiler heatto be on full, and a block 390 lights the "wait" light 234. Thiscontinues until the decision block 386 indicates that the boilertemperature is up. A block 392 then shifts boiler temperature to a "low"setting, and a block 394 calls for a "ready" light 236. A decision block396 tests to see if the "start" button 220 has been pressed. If it hasnot, operation cycles in a "ready" mode. If "start" is engaged, adecision block 398 tests to see if the door 22 is closed. If it is not,a block 400 assures that the blower 82 is off, and a block 402interrupts power to the boiler heating elements 68, 140 and 142. If thedoor 22 is closed, a block 404 calls for operation of the blower 82, anda block 406 starts the timer. A decision block 408 tests whether thetimer has timed out. If it has not, the steam cycle continues. If thetimer has timed out, a block 410 turns off the blower 82 and the boilerheat. A block 412 calls for the buzzer to sound for a predeterminedtime, and a stop circle 414 indicates that the cooking operation isended. The steam mode is operated so as to require the use of a timer.This is a matter of design choice.

FIG. 16 is a flow chart of operation in the hold or proof mode. In FIG.16, a selection block 420 indicates that hold or proof has been selectedby dial 242. This entry may be made as a result of timing out from theuse of one of the oven modes, or it may be entered directly. Directentry is the usual way for using the oven to proof dough. It may also bedesirable to cook under conditions of controlled humidity or at thelower temperature available in the hold of proof mode. In any event,then the hold or proof mode is entered, as indicated by the selectionblock 420, a block 422 checks to see that the blower 82 is on, and ablock 424 checks to see that the hold temperature has been set by dial242, while a block 426 checks to see that hold time is set. A decisionblock 428 then test to see if a humidity setting has been made by dial246. If a humidity setting is made, a block 430 calls for a reading ofboiler temperature, and a block 432 calls for the oven temperature.These are essentially wet- and dry-bulb readings which can be taken to alook-up table in ROM 268 or EEPROM 272 or the like, from which a block434 calculates the humidity in the oven. A decision block 436 testswhether the humidity is within limits. If it is not, a decision block438 tests to see if the humidity is high. If it is, this means that theboiler temperature is too high and a block 440 calls for blowdown. Thisrepresents opening the solenoid valve 100 and admitting cold water untilthe boiler temperature is at a proper value. Level control means 282connected to level sensor 74 controls the means for supplying water(solenoid valve 100) and the means for draining water (solenoid value120) to control the level of water in the boiler by blowdown andreplacement until the boiler temperature is at the proper value. If thehumidity is not in limits and is not high, the 432 selects low boilerheat. When the decision block 436 indicates that the humidity is inlimits, a block 444 calls for the boiler heat to be turned off. Controlthen passes to decision a block 446, which tests to see if the oventemperature is in limits. If it is, and if a decision block 448indicates that the hold timer is running, then a block 450 calls for lowoven power and the control cycle repeats. If the hold timer times out,control passes to an off circle 452, and the oven is turned off. If thedecision block 446 receives in indication that the oven temperature isout of limits, a decision block 454 tests to see if the temperature ofoven chamber 52 is high. If it is, a block 456 calls for oven power tobe turned off, and control is in this mode until the temperature of ovenchamber 52 again comes within limits. If the temperature of oven chamber52 is out of limits and is not high, then the decision block 454 passescontrol to a block 458, which calls for high oven power.

FIG. 17 is a flow chart showing the control of boiler water level. Aselection block 470 indicates that boiler water is called for incooking. This means that the combo oven is either in the combo or steammode. If the combo oven is operated in the oven mode, boiler water isnot called for, and the boiler is empty with the clamp valve 120 open.The boiler water is called for by operation of a decision block 472which tests whether high water level is sensed in the boiler. If it isnot, a decision block 474 tests to see whether a low water level issensed in the boiler. If it is, a block 476 orders the solenoid valve100 opened. If the low level is not sensed, a block 478 calls for thewater to be turned off in the boiler. A block 480 times the fill, as theboiler is allowed a set time to fill. If the time is out of limits, adecision block 482 calls for a shutdown circle 484, and the oven is shutdown. If the time of fill is within limits, control returns to thedecision block 472. If the high level is sensed, a block 486 directsthat the water valve be closed. A decision block 488 then tests whetherthe low level is sensed. If the low level is not sensed by the decisionblock 488 when the high level is sensed by the decision block 472, thena block 490 detects that there is an error in the sensors. One or moreof the sensors may have failed. A block 492 directs the display of inerror signal, and shutdown signal 494 shuts the oven down. If the lowlevel is sensed in the decision block 488, control returns to thedecision block 472, and the cycle continues.

FIG. 18 is a flow chart showing the operation of the cooldown mode forthe combination oven. In FIG. 18, a selection block 500 indicates thatthe cooldown mode has been activated. This is done when one of themodes, steam, combo, or oven has been selected. A decision block 502tests whether the door 22 is open. If it is not the cooldown mode hasnot been selected, and a block 504 directs exit. If the door is open, adecision block 506 tests whether the "hot" light 238 is on. This is anindication that the temperature setting has been changed to a lowervalue, calling for oven cooldown. If the "hot" light 238 is not on, ablock 508 directs exit from the cooldown mode. If the "hot" light 238 ison, a block 510 tests to see if the "start" button 220 has beendepressed. Depressing the "start" button in a hot oven with the door 22open causes a block 512 to turn the heater off and a block 514 to runthe blower 82. This speeds the cooldown process which continues as longas the oven chamber 22 is above the new set temperature. When the ovenchamber 52 is cooled to the new set temperature, the decision block 506directs control to the block 508, which exits from the cooldown mode.

FIG. 19 is a combination front, side and bottom view of the shroud 60 ofthe present invention. The shroud 60 comprises a wall section 600 thatincludes an opening 602 through which the blower 82 of FIG. 3 circulatesair that is heated by the heating elements 86, 88 and 90 of FIG. 3. Endwalls 604 and 606 include cutouts 608 and 610 in the end wall 604, andcorresponding cutouts (not shown) in the end wall 606 that are adaptedto hang the shroud 60 on pins inside the oven chamber 52. The shroud 60is hung by the cutouts 608, 610, and the corresponding cutouts in theend wall 606. The opening 602 serves as a blower shroud to guide air toblower 82. At the same time, the plenum 60 is readily lifted and removedfor cleaning and for access to the boiler 66 of FIG. 2.

FIG. 19 also gives detailed view of the rack 56 which is seen to provideseven shelf supports 612. Risers 614 and 616 serve to space shelves awayfrom shroud 60 to improve the circulation of air in the oven chamber 52.

FIG. 20 is a combination top, side, and end view of the shelf 72 of FIG.2. The shelf 72 comprises a pair of side rods 624 and 626 that engagethe shelf support 612 of FIG. 19 to support the shelf 72. A plurality ofsupport rods 628 supports trays in position in the combination oven 20,and these trays are spaced away from the interior of the oven 20 by apair of spacer rods 630 and 632. The spacer rods 630 and 632 maintainfree circulation of air within the combination oven 20. The shelf 72 iskept from tipping by a pair of hooks 634 and 636 that engage the racks54 and 56 of FIG. 2.

FIG. 21 is a sectional view through the center of the shaft of theblower 82 of FIG. 3. In FIG. 21, a shaft 644 is connected to a motorwhich is not shown. A hub 646 is pressed on the shaft 644 to coupletorque to the blower 82. The screw 84 is sized to fit the threads 648 inthe hub 646 and press against the shaft 644 to separate the shaft 644from the hub 646. A key 650 assists in preventing relative turningmotion between the hub 646 and the shaft 644.

FIG. 22 is a connection diagram showing the means of achieving differentlevels of heating power using the same relays for single-phase power andthree-phase power that is supplied to the boiler heating elements 68,140 and 142. In FIG. 22, a terminal block 660 is adapted either to bringin single-phase ac power on lines 662 and 664 or else to bring inthree-phase power on lines 662, 664 and 666. A connection plug 668 isshown here in a position to select single-phase ac. The position 670,shown in dotted lines, selects single-phase power. The relay contacts672, 674, 676, 678 and 680 are operated as follows to make differentconnections to the boiler heating elements 68, 140 and 142. When all thecontacts 672-680 are open, no power is supplied to the heating elements68, 140 and 142. When the relay contacts 672, 674, 676 and 678 areclosed and the relay contact 680 is open, each of the heating elements68, 140 and 142 receives full voltage and each delivers three kilowattsfor a total boiler power of nine kilowatts. This is applied during thesteam mode and during the period when the combo oven 20 is beginning toheat. With the relay contacts 672, 676 and 678 open and the relaycontacts 674 and 680 closed, the heating elements 68 and 140 are placedin series across the ac voltage, supplying a total of 1.5 kilowatts.

The combination oven 20 of the present invention operates in response tomanual inputs and also to inputs from various sensors. These inputs arecoupled to the microprocessor where they are processed to control numberof quantities and also to produce display information. Table 1 is a listof the parameters sensed in combination oven 20.

TABLE 1

Parameters Sensed in Combination Oven 20

Temperature in oven Chamber 52

Water High Level in Boiler 66

Water Low Level in Boiler 66

Water Temperature in Boiler 66

Over Temperature in Oven Chamber 52

Temperature of Liquid in Drain Line 96

Light at relay contact

Table 2 is a list of the switches and controls, both manually andautomatically operated, that provide inputs to control combination oven20. It should be noted that the combination oven 20 can be operatedwithout the proof and hold feature. If this is done, certain of thefeatures of Tables 2, 3 and 4 will not be needed.

TABLE 2 Switches and Controls in Combination Oven 20

On-OFF

Mode: Steam, Combination, Oven

Oven Temperature

Time

Holding Temperature

Holding Humidity

Start

Clear

Door Open

Table 3 is a list of the quantities and elements controlled by themicroprocessor of the present invention in response to the inputs fromthe sensed parameters of Table 1 and the switches and controls of Table2. The microprocessor used was an Intel 8031.

TABLE 3 Items Controlled in Combination Oven 20

Water Level in Boiler 66

Air Temperature in Oven Chamber 52

Humidity in Oven Chamber 52

Electric Power to Boiler Heating Elements 68

Electric Power to Oven Chamber Heating Elements 86, 88 and 90

Boiler Temperature

Boiler Blowdown

Time to Fill Boiler

Over Temperature

Cooking Time

Holding Temperature

Drain Valve

Condensate Spray

Timing at Relay Closing & Opening

The microprocessor of the present invention controls various displays toassist an operator of the combination oven 20. Table 4 is a list ofthose displays.

TABLE 4 Displays in Combination Oven 20

Cooking Time

Service

Hot

Ready

Wait

Steam

Combo

Oven

On

Cooking Temperature

Holding Temperature

Humidity

Alert Buzzer (cooking timeout)

Colon Flash (timer running)

The description of specific embodiments of the present invention isintended to set forth the best mode known to the inventors for thepractice of their invention. It should be taken as illustrative and notas limiting, and the score of the invention should be limited only bythe appended claims.

What is claimed is:
 1. Apparatus for controlling humidity in a chamber,such as a proofing oven, which comprises:(a) an enclosure; (b) a chamberwithin the enclosure; (c) a vaporizing compartment disposed within theenclosure in vapor communication with said chamber; (d) means forsupplying water to said vaporizing compartment; (e) means for heatingwater within said vaporizing compartment to produce water vapor; (f)means for draining water from said vaporizing compartment; (g) meansdisposed within the chamber for sensing dry-bulb temperature within saidchamber; (h) means for sensing web-bulb temperature within saidvaporizing compartment by sensing the temperature of water within saidcompartment; (i) heating means disposed in said chamber to heat gas andwater vapor within the chamber; (j) a blower fan disposed to circulategas and water vapor in the chamber through the chamber heating means toheat the chamber; (k) means disposed in the enclosure and outside of thechamber for controlling said chamber heating means in response to senseddry-bulb temperature; (l) means for sensing a level of water within saidvaporizing compartment; (m) means operatively connected to said levelsensing means for controlling the means for supplying water and themeans for draining water to control a desired level of water in thevaporizing compartment; and, (n) means operatively connected to saiddry-bulb temperature sensing means, to said wet-bulb temperature sensingmeans, to said water heating means, and to said water level controllingmeans to control a desired humidity within said chamber by heating waterwithin the vaporizing compartment when the humidity is too low, and byintroducing cold water into said compartment and draining hot watertherefrom when the humidity is too high.
 2. Apparatus according to claim1 wherein said compartment is disposed within said chamber.
 3. Apparatusaccording to claim 1 wherein said compartment is disposed along a wallof said chamber.
 4. Apparatus according to claim 3 wherein saidcompartment is disposed within said chamber.
 5. Apparatus according toclaim 1 wherein said water heating means comprises an electrical heatingmeans.
 6. Apparatus according to claim 1 wherein said chamber heatingmeans comprises an electrical heating means.
 7. Apparatus according toclaim 1 further comprising:(a) a microprocessor; and, (b) electroniccircuitry operatively connected to said microprocessor for receivinginputs from said dry-bulb and wet-bulb temperature sensing means andfrom said water level sensing means to process information to controlsaid water level control means and said water heating means to maintainsaid desired water level and said desired humidity.
 8. Apparatus forcontrolling humidity in a chamber, such as a proofing oven, whichcomprises;(a) an enclosure; (b) a chamber within the enclosure; (c) avaporizing compartment disposed within the enclosure in vaporcommunication with said chamber; (d) means for supplying water to saidvaporizing compartment; (e) means for heating water within saidvaporizing compartment to produce water vapor; (f) means for drainingwater from said vaporizing compartment; (g) means disposed within thechamber for sensing dry-bulb temperature within said chamber; (h) meansfor sensing web-bulb temperature within said vaporizing compartment; (i)means for sensing a level of water within said vaporizing compartment;(j) means operatively connected to said level sensing means forcontrolling the means for supplying water and the means for drainingwater to control a desired level of water in the compartment; and, (k)humidity control means operatively connected to said dry-bulbtemperature sensing means, to said wet-bulb temperature sensing means,to said water heating means, and to said water level controlling meansto control a desired humidity within said chamber.
 9. Apparatusaccording to claim 8 wherein said humidity control means adjusts saidwater heating means to increase water temperature when the humidity istoo low, and opens said water supply means to introduce cold water intosaid vaporizing compartment when the humidity is too high, to therebycause said level control means to open said water drain means to removehot water from said compartment to reduce water temperature. 10.Apparatus according to claim 8 wherein said wet-bulb temperature sensingmeans senses the temperature of water within said compartment. 11.Apparatus according to claim 8 wherein said compartment is disposedwithin said chamber.
 12. Apparatus according to claim 8 wherein saidcompartment is disposed along a wall of said chamber.
 13. Apparatusaccording to claim 12 wherein said compartment is disposed within saidchamber.
 14. Apparatus according to claim 8 wherein said water heatingmeans comprises an electrical heating means.
 15. Apparatus according toclaim 8 further comprising:(a) a microprocessor; and, (b) electroniccircuitry operatively connected to said microprocessor for receivinginputs from said dry-bulb and wet-bulb temperature sensing means andfrom said water level sensing means to process information to controlsaid water level control means and said water heating means to maintainsaid desired water level and said desired humidity.
 16. Apparatusaccording to claim 8 further comprising means for heating gas and vaporwithin said chamber, and temperature control means operatively connectedto said dry-bulb temperature sensing means for controlling said chamberheating means to provide a desired dry-bulb temperature within saidchamber.
 17. Apparatus according to claim 16 wherein said chamberheating means includes an electrical heating means.
 18. Apparatusaccording to claim 16 further comprising:(a) a microprocessor; and, (b)electronic circuitry operatively connected to said microprocessor forreceiving inputs from said dry-bulb and wet-bulb temperature sensingmeans and from said water level sensing means to process information tocontrol said water level control means, said water heating means, andsaid chamber heating means to maintain said desired water level, saiddesired humidity, and said desired dry-bulb temperature.
 19. Method forcontrolling humidity in a chamber, such as a proofing oven, wherein anenclosure contains said chamber and a vaporizing compartment in vaporcommunication with said chamber, which comprises:(a) passing water intosaid compartment by water input means; (b) maintaining a water levelwithin said compartment by level control means generating a signalindicative of water level; (c) heating water within said compartment bywater heating means sufficiently to generate water vapor; (d) passingwater vapor from said compartment into said chamber; (e) sensingtemperature in said chamber by means generating a signal indicative ofdry-bulb temperature; (f) sensing temperature in said compartment bymeans generating a signal indicative of web-bulb temperature; (g)passing said water level signal, said dry-bulb temperature signal, andsaid wet-bulb temperature signal to a humidity control means containingsetting adjustment means for establishing a desired humidity to becontrolled; (h) passing a signal from said humidity control means tosaid water heating means when said dry-bulb and wet-bulb temperaturesindicate that the humidity in said chamber is below the desired humidityto cause heat to be applied to water in said compartment for increasingthe generation of water vapor; and (i) passing a signal from saidhumidity control means to said water input means to allow cold water topass in to said compartment to cool the water in said compartment whenthe dry-bulb and wet-bulb temperature signals indicate that the humidityin said chamber is above the desired humidity, and thereby cause saidlevel control means to remove hot water from said compartment to reducethe water temperature.
 20. Method according to claim 19 wherein saidchamber includes chamber heating means and temperature control meansincluding setting adjustment means for establishing a desired chambertemperature, and said method further includes the steps of passing saiddry-bulb temperature signal to said temperature control means passing asignal from said temperature control means to said chamber heating meansto increase heat input to said chamber when said dry-bulb temperature isbelow said desired chamber temperature and to decrease heat input tosaid chamber when said dry-bulb temperature is above said desiredchamber temperature.
 21. Method according to claim 19 wherein saidsignal indicative fo wet bulb temperature is generated bysensing thetemperature of water in said compartment.